Java设计模式 - 组合模式

布满荆棘的人生 2022-11-24 11:29 154阅读 0赞

**目录**

组合模式：

组合优点：

组合模式应用：

组合实例：

上述代码 GitHub 地址：https://github.com/baicun/designPatterns

--------------------

# [组合模式：][Link 1] #

处理具有树形结构的设计模式，具体使用一致的方式来处理个别对象以及不同对象组合。

# [组合优点：][Link 2] #

兼容性强，不必关心处理的是单个对象还是整个组合结构

# [组合模式应用：][Link 3] #

java.AWT Component中的组合模式

# [组合实例：][Link 4] #

类图：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NzZG5fMDkxMQ_size_16_color_FFFFFF_t_70][]

示例：俩家不同的餐馆合并，需要打印出不同组合的菜单，面包馆呢是遍历的集合，而小饭馆呢是遍历的数组，所以需要找一个统一的方法，来解决这个问题，之前使用的迭代器模式进行设计，现在想在小饭馆菜单中增加饭后甜点，他和小饭馆菜是菜单包含菜单，我们称之为容器，这个时候，就需要使用组合模式。

代码：

创建一个大的容器类-MenuComponent.java

public abstract class MenuComponent {
    
    	public String getName() {
    		return "";
    	}
    
    	public String getDescription() {
    		return "";
    	}
    
    	public float getPrice() {
    		return 0;
    	}
    
    	public boolean isVegetable() {
    		return false;
    	}
    
    	public abstract void print();
    
    	public Iterator getIterator() {
    		return new NullIterator();
    	}
    }

面包馆菜单-CakeHouseMenu.java

public class CakeHouseMenu extends MenuComponent {
        private ArrayList<MenuComponent> menuItems;
    
        public CakeHouseMenu() {
            menuItems = new ArrayList<MenuComponent>();
    
            addItem("KFC Cake Breakfast", "boiled eggs&toast&cabbage", true, 3.99f);
            addItem("MDL Cake Breakfast", "fried eggs&toast", false, 3.59f);
            addItem("Stawberry Cake", "fresh stawberry", true, 3.29f);
            addItem("Regular Cake Breakfast", "toast&sausage", true, 2.59f);
        }
    
        private void addItem(String name, String description, boolean vegetable,
                             float price) {
            MenuItem menuItem = new MenuItem(name, description, vegetable, price);
            menuItems.add(menuItem);
        }
    
        public Iterator getIterator() {
            return new ComposeIterator(menuItems.iterator());
        }
    
        @Override
        public void print() {
            System.out.println("****This is CakeHouseMenu****");
        }
    }

小饭馆菜单-DinerMenu.java

public class DinerMenu extends MenuComponent {
        private final static int Max_Items = 5;
        private int numberOfItems = 0;
        private MenuComponent[] menuItems;
    
        public DinerMenu() {
            menuItems = new MenuComponent[Max_Items];
            addItem("vegetable Blt", "bacon&lettuce&tomato&cabbage", true, 3.58f);
            addItem("Blt", "bacon&lettuce&tomato", false, 3.00f);
            addItem("bean soup", "bean&potato salad", true, 3.28f);
            addItem("hotdog", "onions&cheese&bread", false, 3.05f);
            // 新增饭后甜点
            addSubMenu(new SubMenu());
    
        }
    
        private void addItem(String name, String description, boolean vegetable,
                             float price) {
            MenuItem menuItem = new MenuItem(name, description, vegetable, price);
            if (numberOfItems >= Max_Items) {
                System.err.println("sorry,menu is full!can not add another item");
            } else {
                menuItems[numberOfItems] = menuItem;
                numberOfItems++;
            }
    
        }
        private void addSubMenu(MenuComponent mMenuComponent) {
            if (numberOfItems >= Max_Items) {
                System.err.println("sorry,menu is full!can not add another item");
            } else {
                menuItems[numberOfItems] = mMenuComponent;
                numberOfItems++;
            }
    
        }
    
        public Iterator getIterator() {
            return new ComposeIterator(new DinerIterator());
        }
    
        class DinerIterator implements Iterator {
            private int position;
    
            public DinerIterator() {
                position = 0;
            }
    
            @Override
            public boolean hasNext() {
                // TODO Auto-generated method stub
                if (position < numberOfItems) {
                    return true;
                }
                return false;
            }
    
            @Override
            public Object next() {
                // TODO Auto-generated method stub
                MenuComponent menuItem = menuItems[position];
                position++;
                return menuItem;
            }
    
            @Override
            public void remove() {
                // TODO Auto-generated method stub
            }
        }
    
        @Override
        public void print() {
            System.out.println("****This is DinerMenu****");
        }
    }

饭后甜点-SubMenu.java,集成超类，方便遍历子元素。

public class SubMenu extends MenuComponent {
    	private ArrayList<MenuComponent> menuItems;
    
    	public SubMenu() {
    		menuItems = new ArrayList<MenuComponent>();
    
    		addItem("Apple Cookie", "Apple&candy&Cookie", true, 1.99f);
    		addItem("Banana Cookie", "Banana&candy&Cookie", false, 1.59f);
    		addItem("Orange Cookie", "Orange&Cookie", true, 1.29f);
    	}
    
    	private void addItem(String name, String description, boolean vegetable,
    			float price) {
    		MenuItem menuItem = new MenuItem(name, description, vegetable, price);
    		menuItems.add(menuItem);
    	}
    
    	public Iterator getIterator() {
    		return new ComposeIterator(menuItems.iterator());
    	}
    
    	@Override
    	public void print() {
    		System.out.println("****This is SubMenu****");
    	};
    	// 其他功能代码
    
    }

测试类：

public class MainTest {
    	public static void main(String[] args) {
    		Waitress mWaitress = new Waitress();
    		CakeHouseMenu mCakeHouseMenu = new CakeHouseMenu();
    		DinerMenu mDinerMenu = new DinerMenu();
    		mWaitress.addComponent(mCakeHouseMenu);
    		mWaitress.addComponent(mDinerMenu);
    		mWaitress.printVegetableMenu();;
    	}
    }

# [上述代码 GitHub 地址：https://github.com/baicun/designPatterns][GitHub _https_github.com_baicun_designPatterns] #

[Link 1]: https://blog.csdn.net/csdn_0911/article/details/107823211#%E4%BB%A3%E7%90%86%E6%A8%A1%E5%BC%8F%EF%BC%9A-toc-toc-toc-toc-toc-toc-toc-toc
[Link 2]: https://blog.csdn.net/csdn_0911/article/details/107823211#%E8%BF%AD%E4%BB%A3%E5%99%A8%E4%BC%98%E7%82%B9%EF%BC%9A
[Link 3]: https://blog.csdn.net/csdn_0911/article/details/107823211#%E8%BF%AD%E4%BB%A3%E5%99%A8%E6%A8%A1%E5%BC%8F%E5%BA%94%E7%94%A8%EF%BC%9A
[Link 4]: https://blog.csdn.net/csdn_0911/article/details/107823211#%E8%BF%AD%E4%BB%A3%E5%99%A8%E5%AE%9E%E4%BE%8B%EF%BC%9A
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NzZG5fMDkxMQ_size_16_color_FFFFFF_t_70]: /images/20221124/1b9bf81e68e344b6a533e54bdfaaa036.png
[GitHub _https_github.com_baicun_designPatterns]: https://blog.csdn.net/csdn_0911/article/details/107823211#%E4%B8%8A%E8%BF%B0%E4%BB%A3%E7%A0%81%20GitHub%20%E5%9C%B0%E5%9D%80%EF%BC%9Ahttps%3A%2F%2Fgithub.com%2Fbaicun%2FdesignPatterns